1. Field of the Invention
The present invention relates to methods for real-time or near real-time distribution of medical telemetry data over a computer network. More particularly, the present invention relates to a network architecture for facilitating the efficient and reliable exchange of information between portable wireless patient monitoring devices and computers located throughout a hospital.
2. Description of the Related Art
Medical telemetry systems that allow physiologic data from multiple, remotely-located patients to be monitored from a central location are known in the art. These systems typically comprise remote telemeters that remotely collect the physiologic data of respective patients and transmit the data over a wireless link to a monitoring station. This physiologic data may include, for example, real-time electrocardiograph (EKG) waveforms, CO2 levels, blood pressure, temperature, SO2 levels, respiration rates, etc. From the monitoring station, a clinician can, in real-time, visually monitor the physiologic status of many different patients. The central station may also run automated monitoring software for alerting the clinician whenever a predetermined physiologic event occurs, such as a cardiac arrhythmia condition.
The remote telemeters of medical telemetry systems are generally of two types: instrument remote telemeters and ambulatory remote telemeters. An ambulatory remote telemeter is a portable, battery-powered device which permits the patient to be monitored while the patient is ambulatory. The ambulatory telemeter attaches to the patient by a strap or other attachment device, and receives the patient's physiologic data via EKG leads (and/or other types of sensor leads) which attach to the patient's body. The physiologic data is continuously transmitted to the central monitoring station by the telemeter's radio frequency (RF) transmitter to permit real-time monitoring. Instrument remote telemeters operate in a similar manner, but receive the patient's physiologic data from a bedside monitor (or other instrument) over a hardwired line, such as an RS-232 connection. Instrument remote telemeters that transfer the physiologic data to the monitoring station over a hardwired connection are also found.
Typically, the monitoring station includes a receiver for receiving and decoding the RF transmissions from the patient transmitter, and a computer for displaying the physiologic data. In many cases, the receivers are implemented as circuit boards that plug into a standard personal computer. The resulting physiologic data is displayed on the computer screen. In these applications, the process of collecting data and updating the display is relatively simple because the receiver, computer, and display are combined in a single system. Unfortunately, this type of non-networked system does not make the patient telemetry data available throughout the hospital.
For example, a monitoring station is usually placed at a nurse's station near the patient's room. If a physician, whose office is located in a different wing of the hospital, needs to view the patient's EKG, then the physician must visit the nurse's station where the data is being displayed. Another problem with non-networked monitoring is that inadequacies in the non-networked system architecture make it impractical to monitor a large number of patients (e.g., 500 to 800 or more).
Prior attempts to use computer networks to facilitate the display of physiologic telemetry data have been cumbersome and expensive because of the real-time nature of the data and the volume of data involved. In such systems, the central station consists of a receiver connected to a computer, which operates as a proprietary network data server. The data is transmitted over a dedicated network, using proprietary hardware and software, to various workstation computers (workstations) located elsewhere in the hospital. This type of system has the advantage of providing access to patient data, but at the expense of installing a custom computer network that is dedicated solely to telemetry data. Again, use of a dedicated network was necessary because of the real-time nature of the data, the volume of data, and the critical nature of the data. Even in situations, such as private networks (Intranets), where the delays introduced by other network traffic can be controlled, the overhead associated with standard protocols, such as HTTP, is often prohibitive.
It is well known to those skilled in the art of computer operating systems and networks, that the methods for handling real-time data are markedly different from those used to handle non-real-time data. Most computer operating systems are not designed to handle real-time data well. Computer operating systems that are designed to handle real-time data are generally special purpose operating systems not intended for general use. The data from most telemetry systems, including medical telemetry systems, occurs in a continuous stream, and typically must be received continuously. The operating system cannot command the sending device to stop sending the data for any appreciable length of time owing to the time critical nature of the data. For example, in a medical telemetry system that monitors patient EKG waveforms, the clinician must be notified immediately of any emergency conditions. Thus any computer, or computer network, designed to handle medical telemetry data must be capable of processing the data without undue delay. True real-time processing may not be necessary, but the processing must be close to real-time (near-real time or quasi-real time).
Standard computer networks, meaning networks that employ readily available hardware and software components (e.g., the Internet), are also typically not designed to deliver data in real-time. Standard networks, such as the Internet, are designed to deliver data as quickly as possible, but not on any set schedule. For instance, it is well known to one skilled in the art that a user downloading a large file over the Internet will typically see the data arrive in bursts separated by varying time delays. The amount of time required for a message to travel from a sending computer to a receiving computer is known as latency time. In a packet-switching network (PSN) such as the Internet, data is usually read and forwarded by several routers before it reaches its destination. No effort is made to establish a single electrical circuit between two computing devices. Instead, the sending computer divides a message into a number of efficiently sized units called packets. Each packet contains the address of the destination computer. These packets are then broadcast to the network. The packets are received by devices called routers that read each packet's destination address and, based on that address, forward the packets in the appropriate direction. Eventually, the packets arrive at their intended destination, although some may have actually traveled by different physical paths. The receiving computer assembles the packets, puts them in order, and delivers the received message to the appropriate application. Packet-switching networks are highly reliable and efficient, but they are not generally suited to the delivery of real-time data because the routing process results in variable latency times (known as jitter).